This winter I've decided to get rid if those slackish stock wheels on my boat trailer, and throw on either the gear 726's or XD hoss, which are on my truck.
I want to go with 20's, but I see quite a few with 18's. Would it be wiser to roll with 18's?

I just upgraded my trailer from 14" wheels to 18" (bought the wheels pdxWAKE on here was selling that he had on his Supra trailer). In my opinion, the 18" wheels are the best diameter for a trailer...I wanted the wheels I bought before they were ever for sale and only wanted 18's. 17's look a bit too small and 20"+ just look off.

Also, a 255/55/18 would be too tall of a tire. Mine has what Boatmate and other brands are running from the factory: Nexen N3000 in a 245/45/18. These specific tires in this specific size have a much higher load rating than most other tires around their size (1929 instead of the 1400-1600 seen in most other tires). In the end it is overkill as my boat/trailer combo is right around 5000 on a dual axle trailer, so even a 1400 rating would be enough. But these are passenger tires on a trailer, so no harm in a margin of safety.

These tires end up being almost 1" taller than the 205/75/14 tires that are being replaced. Everything fits fine except I have to replace the fenders; very minor rubbing on the back side I can easily fix but the tires are too wide and I have teardrop fenders so it would look very odd rolling them. 10.75" fenders are NOT cheap, so don't forget to factor that into the cost. Here is a single shot of mine mounted with the old fenders as I haven't got new ones yet since she is parked in the garage for the winter.

Thanks for the pics and info fellas!
I found another thread on here, some folks are running 225 45 18 and aren't having rubbing issues with stock fenders.
I'd really like to avoid replacing fenders if possible

I would highly suggest checking out the load rating of those narrower tires before pulling the trigger. These passenger tires at narrower widths tend to have a much lower load rating (which makes sense, since they were designed to fit under smaller cars).

Remember that load rating (combined) needs to be more than the boat/trailer/gear. Also, a number of boat manufacturers underrate their boat weights so your boat may/may not be heavier than you think.

Bumping this back up top for some folks, if there are any, to show off their trailers with the moto metal 962's on them in 18's.
I'm sick of waiting for gear alloy 726 to become available.
They are currently in a lawsuit and all models of the rim have been held to the shelf and cannot be sold.
It is some kind of design lawsuit, I'm guessing with moto metal, since gear basically straight copied the 962.

So if you've got em, throw em up!
I've found a set of 18x9 962 in black for $740 shipped, lowest so far. If anyone has them don't be shy to share a better deal!

Well, just got off the phone with Rimzone. Pulled the trigger on a set of moto metal 962 18's in black.

Now I need to find some tires. I found a set of fuzion tires on tirerack for $90/ea with a combined load rating over. 7k lbs. well over what I'll need for my v215.
Any other budget friendly recommendations?

I have 20's on my Illusion trailer and there are some pro's and con's to having 20's. First, they look awesome IMO, next they handle amazing and the trailer really tracks well with them. I've pulled a couple of trailers with 18's and there is a noticeable difference. I believe it is because of the tire width(275's on the 20's). There is also the fact that you don't have to worry about trailer blowout's as much. 18"/20" tires are speed rated for well over 100 mph so if you live in a 75mph zone like I do, no worries about that speed being too much for the tires.

Cons - the boat sits up quite a bit higher so it's not as easy to load items onto the boat when it's on the trailer. My main issue with the 20's is that I did belong to a lake that has a very shallow grade and because of those 20's, the water would be at the door sill by the time I could actually get the boat off of the trailer. Then loading it was rough on the bunks because I could only go so deep with the truck. I went through 3 sets of trailer bunks in 3 years after I joined the lake due to the shallow loading. If I had 14's or 15's, it wouldn't have been an issue.

Thought I'd update this, you guys convinced me. I got the nexens.
Even though all things being equal on a few less expensive tires. I started doing the math and these are proven.
Cheapest I found was onlinetires.com at $101.90/ea